1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head for ejecting liquid such as ink.
2. Description of the Related Art
Liquid ejection heads are generally manufactured by laying the second substrate that operates as a cover plate having liquid ejection ports on the first substrate that operates as a base plate having a liquid supply port including apertures and grooves by way of an adhesive agent. For this reason, a step of continuously applying a liquid material such as an adhesive agent on the surface of the first substrate with a predetermined width is required for manufacturing liquid ejection heads.
When applying a liquid material such as an adhesive agent continuously on the surface of the first substrate with a predetermined width, liquid of the above described type is more often than not applied in advance to the surface of a cylindrical member and then transferred onto the first substrate. However, this technique is accompanied by problems as will be specifically described below.
FIG. 8A illustrates an exemplar first substrate that has a surface representing an asymmetric layout relative to center line M of a belt-shaped transfer region having a predetermined width W onto which transfer liquid is to be continuously applied. The first substrate 102 that operates as transfer medium has a plurality of grooves 101 for forming a supply port and the plurality of grooves 101 are arranged asymmetrically relative to the center line M of the belt-shaped transfer region having the predetermined width W.
Then, transfer liquid is continuously transferred onto the first substrate 102 in a transfer direction with a predetermined width as illustrated in FIG. 8B. More specifically, a predetermined quantity of transfer liquid 105 has been applied onto the surface of transfer body 103 and the transfer liquid 105 that has been applied onto the surface of the transfer body 103 is then continuously applied onto the first substrate 102 with the predetermined width while the transfer body 103 is pressing the first substrate 102 with predetermined load F.
Under this condition, the pressing force F pressing the transfer liquid 105 acts evenly and uniformly in the short-side direction of the first substrate 102 in the cross section taken along line 9A-9A of the first substrate 102 because no grooves 101 are formed there as illustrated in FIG. 9A.
On the other hand, grooves 101 are formed in the cross section taken along line 9B-9B of the first substrate 102 as illustrated in FIG. 9B. Therefore, the load F that presses the transfer liquid 105 does not act evenly and uniformly on the first substrate 102 and the pressure in the grooves 101 rises. Thus, the first substrate 102 can be inclined as illustrated in FIG. 9C when the force holding the first substrate 102 is weak. Then, as a result, there can arise a problem that no transfer liquid 105 is transferred onto the first substrate 102 at the side thereof that is held apart from the transfer body 103.
When the force holding the first substrate 102 is even and uniform, the first substrate 102 dips deeper into the transfer liquid 105 in the cross section taken along line 9D-9D as illustrated in FIG. 9D if compared with the cross section 9A-9A where no grooves 101 are formed. Then, as a result, there can arise a problem that transfer liquid 105 adheres to the inner walls of the grooves 101.
Thus, when the first substrate 102 has grooves 101 extending in a transfer direction in which transfer liquid 105 is to be continuously applied, the pressing force that acts on the transfer liquid 105 that exists between the first substrate 102 and the transfer body 103 varies as a function of the number of grooves 101. Then, as a result, transfer liquid 105 cannot be applied under the same transfer conditions over the entire surface of the first substrate 102.
Additionally, the pressing force acting on the transfer liquid 105 in the protruding portions in the regions where grooves 101 are formed is greater than the pressing force in the flat regions where no grooves 101 are formed so that the transfer liquid 105 is encouraged to enter deep into the grooves 101 to consequently give rise to a defective transfer of the liquid.
For the above identified reasons, techniques as disclosed in Japanese Patent Applications Laid-Open Nos. 2007-223173 and H10-100419 and described below have been and being employed when continuously applying liquid onto a transfer medium with a predetermined width.
(1) When the transfer medium has a surface representing a symmetric layout relative to the center line of the transfer width thereof, a technique of keeping the transfer pressure applied to the transfer medium in the transfer region to be even and uniform by making the pressure acting on the transfer body (roller or squeegee) operating for a continuous liquid transfer variable so as to be responsive to the surface layout of the transfer medium can be employed.
(2) When the transfer medium has a surface representing an asymmetric layout relative to the center line of the transfer width thereof, a technique of keeping the transfer pressure to be even and uniform by arranging separate transfer mediums onto which transfer liquid is to be applied continuously at the respective opposite sides relative to the center line of the overall transfer width and making the pressures acting on the respective transform mediums variable so as to be responsive to the surface layouts of the transfer mediums can be employed.
(3) When the transfer medium has a surface representing an asymmetric layout relative to the center line of the transfer width thereof, a technique of writing with liquid on a transfer medium by means of a dispenser in a manner responsive to the surface layout of the transfer medium can be employed.
However, the technique of (1) described above has a disadvantage that it can be employed only when the surface layout of a transfer medium is transversally symmetric and the technique of (2) described above has a disadvantage of requiring the use of separate transfer bodies at the opposite sides relative to the center line of the overall transfer width, while the technique of (3) described above has a disadvantage of requiring a long time for the step of applying liquid to a transfer medium, although it provides an advantage of being applicable to transfer mediums having a complex surface layout. Therefore, the object of the present invention is to provide a method of manufacturing a liquid ejection head by using a technique that is free from the above disadvantages and very suited for continuously applying a liquid material such as an adhesive agent to the first substrate of a liquid ejection head that operates as base plate with a predetermined width.